Depolarizing glycine responses in Cajal-Retzius cells of neonatal rat cerebral cortex

• Published in: Neuroscience 2002-01, Vol.112 (2), p.299-307
• Main Authors: Kilb, W., Ikeda, M., Uchida, K., Okabe, A., Fukuda, A., Luhmann, H.J.
• Format: Article
• Language: English
• Subjects: Animals; Animals, Newborn; bicarbonate; Bicarbonates - metabolism; Biological and medical sciences; Cell Membrane - drug effects; Cell Membrane - physiology; Central nervous system; Cerebral Cortex - cytology; Cerebral Cortex - drug effects; Cerebral Cortex - metabolism; chloride; Chlorides - metabolism; cortical development; Dose-Response Relationship, Drug; Electrophysiology; Excitatory Amino Acid Antagonists - pharmacology; Fundamental and applied biological sciences. Psychology; GABA Antagonists - pharmacology; Glycine - pharmacology; Glycine Agents - pharmacology; gramicidin; Gramicidin - pharmacology; In Vitro Techniques; marginal zone; Membrane Potentials - drug effects; Membrane Potentials - physiology; Neurons - cytology; Neurons - drug effects; Neurons - metabolism; Patch-Clamp Techniques; Rats; Rats, Wistar; Receptors, Glycine - agonists; Receptors, Glycine - antagonists & inhibitors; Receptors, Glycine - metabolism; shunting inhibition; Taurine - pharmacology; Vertebrates: nervous system and sense organs
• ISSN: 0306-4522; 1873-7544
• DOI: 10.1016/S0306-4522(02)00071-4

We investigated the properties of glycine-induced responses in Cajal-Retzius cells, a neuronal cell type essential for the establishment of neocortical lamination. Whole-cell and gramicidin-perforated patch-clamp recordings were performed on visually identified Cajal-Retzius cells in tangential slices from neonatal rat cortex (postnatal days 0–3). With a pipette Cl − concentration of 50 mM, bath application of 1 mM glycine induced a membrane depolarization of 32.8±7.4 mV and a massive decrease in membrane resistance by 88±1.4%. The membrane depolarization was abolished in the presence of the glycinergic antagonists strychnine (30 μM) and phenylbenzene-ω-phosphono-α-amino acid (100 μM), while the GABA A receptor antagonist bicuculline (100 μM) and the glutamatergic antagonist (±)-2-amino-5-phosphonopentatonic acid (60 μM) were without effect, suggesting that the glycine-induced membrane responses were mediated exclusively by the strychnine-sensitive glycine receptor. The EC 50 for activation of glycine receptors was 0.54 mM, 1.62 mM and 2.41 mM, for the glycinergic agonists glycine, β-alanine and taurine, respectively. Since the reversal potential of the glycine-induced currents showed a strong dependency on the intracellular chloride concentration and was virtually unaffected under HCO 3 −-free conditions, the activation of glycine receptors was probably linked to Cl − fluxes with little contribution of HCO 3 − ions. Perforated patch recordings from Cajal-Retzius cells demonstrated that glycine elicited depolarizing responses mediated by Cl − currents which reversed at −41±3.7 mV. In summary, from these results we suggest that Cajal-Retzius cells of the neonatal rat cerebral cortex express functional strychnine-sensitive glycine receptors that mediate depolarizing membrane responses via Cl − efflux.